Validation of a PCM simulation tool in IDA ICE ...

Validation of a PCM simulation tool in IDA ICE dynamic building simulation software using experimental data from Solar Test Boxes Cristina Cornaro – Department of Enterprise Engineering, University of Rome “Tor Vergata” – [email protected] Marco Pierro – Department of Enterprise Engineering, University of Rome “Tor Vergata” – [email protected] Daniele Roncarati – Department of Enterprise Engineering, University of Rome “Tor Vergata”– [email protected] Valerio Puggioni – EnUp srl – [email protected]

Abstract

regarding experimental and theoretical analysis of

This work aims to provide a method to validate a PCM

PCM behavior. It is possible to group these work

tool

implemented

simulation

in

software

a

whole

(IDA

ICE)

building

dynamic

into laboratory experimental activity, outdoor

using

outdoor

experimental activity, numerical and theoretical

measurements coming from Solar Test Boxes (STB).

investigation and studies involving experiments

The STB method was originally conceived by ESTER lab

and theory.

at the University of Rome Tor Vergata, to evaluate

For what concerns laboratory tests various works

thermal

semi

could be found. Most of the works examined

transparent materials in outdoor conditions. In the

regard the evaluation of thermal characteristics of

approach presented here two boxes (reference and test)

gypsum

were equipped with a standard double glass pane. A

PCM tested into simulation chambers and/or tests

PCM pane, provided by RUBITHERM®, was put on the

boxes (Lee at al., 2007, Zhang et al., 2012, Zhang et

floor of the test box. Two monitoring campaigns were

al. 2013, Li et al., 2013, Marchi et al., 2013).

carried out and the thermal behaviour of the box with

Barreneche et al., 2013 incorporate PCMs with

PCM was analyzed and compared with the thermal

Portland cement and gypsum and investigated

behaviour of the reference box. Temperature trends

what was the best PCM quantity to be incorporated

measured inside the “PCM box” were used to validate

for each material tested.

the PCM behaviour provided by the IDA ICE tool,

For what concerns outdoor experimental activity it

comparing measured and simulated data.

is worth mentioning the paper from Tardieu et al.

characteristics

of

transparent

and

boards

containing

microencapsulated

2011 that used two cabins, built in Auckland, New Zealand, one used as reference and one with PCM

1. Introduction

and numerical simulation using Energy Plus, to evaluate the thermal behavior of the two cabins.

Since 1930s Phase Change Materials (PCM) have

Both simulation and experimental data collected

been investigated thanks to the pioneering work of

showed that PCM into wallboards improved

Telkes (Telkes, 1975). Many studies have been

thermal inertia of buildings. From simulations they

conducted on these materials since then but

also concluded that the additional thermal mass of

unfortunately their application did not take off due

PCM can reduce the daily indoor temperature

to technological constraint and costs. However in

fluctuation by up to 4 °C in summer days. Also

the last years interest for PCM has grown up again

Entrop et al., 2011 made experiments using small

and this is confirmed by the recent reviews from

boxes exposed outdoor in Denmark and equipped

Khadiran et al., 2016 and Souayfane et al., 2016.

with different materials among which also PCM.

Many studies can be found in the literature

Their results evidenced that PCM is an excellent

Cristina Cornaro, Marco Pierro, Daniele Roncarati, Valerio Adoo Puggioni

way to store energy and small boxes are effective

2016). In the present study they were used to test

in studying this aspect. Also Su et al., 2012 used a

the thermal performance of a SP21E PCM pane

box to evaluate PCM thermal behavior in China

provided by RUBITHERM® which characteristics

while Sage-Lauck and Sailor, 2014 built a Passive

are listed in Table 1. The STBs were provided with

House duplex in Portland, Oregon. They found

two identical standard double glass panes. In the

that the addition of PCM could reduce the number

experiments one of the boxes (PCM) contained the

hours of over-heating of about 60%.

PCM panel while the other (Ref) was used as

Goia et al., 2014 tested a glazing system filled with

reference.

PCM in outdoor conditions during a long term monitoring campaign. They concluded that the

Table 1 – SP21E PCM pane characteristics

PCM glazing is capable to smooth and shift the

Data

solar gains and that this result could positively

Melting area

22 – 23 °C

contribute to the energy balance of highly glazed

Congealing area Heat Storage Capacity

21 – 19 °C

buildings. Numerical simulation is also used to evaluate PCM

Value

160 kJ/kg

Combination of sensible and latent heat in a temperature range of 13 °C to 28 °C.

performance at different locations and climate

Specific Heat Capacity

2 kJ/kgK

using various simulation tools such as ESP-r

Density solid (15 °C)

1.5 kg/l

(Fernandes e Costa, 2009), self-made programs

Density liquid (35 °C)

1.4 kg/l

(Zwanzig et al., 2013), COMSOL environment

Volume expansion

3–4%

(Zhou et al., 2014) and Energy Plus (Guarino et al.,

Thermal conductivity

2015). All these works should be supported by

Max Operation temperature

0.6 W/mK 45 °C

experimental data as Guarino et al., 2015. The aim of this work is to provide valuable

STBs thermal behaviour was simulated in the IDA

experimental data that could be used to validate

ICE dynamic simulation environment. In particular

the behavior of a custom PCM simulation tool

the “PCM box” model was provided with the

integrated in the whole building simulation

custom PCM software module to simulate the PCM

software IDA ICE by EQUA simulation. In the

pane. Temperature data gathered during two short

following sections the experimental facility used

term outdoor monitoring campaigns, carried out in

for the study is presented together with the custom

different periods of the year, were used to validate

PCM software module implemented in the IDA

the results.

ICE environment. The results of the monitoring campaigns

are

presented

and

a

comparison

between simulated and measured data to validate the tool is discussed. Once validated the software module

could

be

used

to

evaluate

energy

performance of PCM inside buildings.

2.2 Solar Test Boxes description The boxes were designed with a linear scale factor of 1:5 and a surface scale factor of 1:25 with respect to a real room. They have the dimensions of 1.00 m × 0.60 m × 0.55 m and consist of 5 opaque walls and one glazed wall. The exterior was manufactured with plywood panels of 8 mm thickness painted

2. Simulation and experiment

entirely white, to make them highly reflective. The entire not glazed inner surface of the boxes, also

2.1 Method

comprising the portion of the area behind the

Solar Test Boxes (STBs) were built with the

frame of the window, was heavily insulated with a

objective of making comparative analysis

lightweight rigid insulating material of 80 mm

of

thermal and lighting performance of transparent

thickness,

material with respect to a double glass reference

insulation in buildings. On the south facing wall a

pane and to evaluate solar heat gain and U-value

glazed area of 42 cm × 37 cm can be allocated, the

of innovative semi-transparent materials (Cornaro,

remaining of this surface being occupied by a

Stiferite

GT,

specific

for

thermal

Table 2 – Thermal properties of STB materials

Thickness (mm)

Density (kg/m3)

Specific heat (J/kgK)

Thermal conductivity (W/mK)

Thermal resistance (m2K/W)

SHGC

Plywood

8

545

1215

0.120

-

-

Insulation

80

36

1453

0.024 (at 10 °C)

3.33

-

Double glazed pane

20

2400

800

1.4

0.34

0.82

wood frame 90 mm thick, to shield the thickness of

could damage it. For this reason, the original

the inside insulating panes.

glazed area was reduced using a wider wood

Each box is instrumented to measure inside air

frame. A new calibration was then necessary to

temperature, illuminance and surface temperature

take into account for this modification (Figure 1).

of the inner and outer side of the glazed pane. Temperature sensors are TT500 thermistors by Tecno.el srl with a wide temperature range (−30 to 120 °C), a resolution of 0.1 °C and an accuracy of ±0.2 °C. Illuminance is measured using a luxmeter by Delta Ohm srl with a measurement range of 200,000 lx, a sensitivity of 1.5 mV/klx and calibration accuracy less than 4%. Also outside temperature and relative humidity, solar irradiance on the vertical plane and wind speed and direction can be measured using a portable weather station. Temperature and relative humidity are measured by a Rotronic Hygroclip2 sensor with accuracy of ±0.1 °C for temperature and of ±0.8% for relative humidity. Solar irradiance sensor is a silicon cell pyranometer provided by Apogee Instruments with an accuracy of ±5% while wind speed and direction are measured using a model 7911 anemometer provided by Davis Instruments with an accuracy of ±1 m/s for speed and of ±7° for direction. Data are acquired at a minute time rate. The weather and solar station of ESTER lab (Lat. 41.9, Long. 12.6) (Spena et al. 2008) provides direct and diffuse solar irradiance measurements useful for climate file construction in the dynamic simulation software. Table 2 lists the material properties used in STBs.

2.3 STB calibration

Fig. 1 – STBs with different window frames during the calibration test

A short – term monitoring campaign was carried out at ESTER lab from the 12th to the 17 th of November 2015 to collect calibration data. Figure 2 shows the trends of external and inside air temperature monitored in the two STBs equipped with the reference glazed pane and the two different frames. The inside temperature of both boxes raised up to 50° and more, due to the high insulation properties of the materials and the solar heat gain of the glazing. In particular, the inside temperature of the old framed STB (Tair_OF) reached almost 80 °C, or more, while the new framed STB (Tair_NF) did not exceed 50 °C. This difference is explained by the reduction of the glazed surface due to the new frame. First of all the air temperature trend inside the old

STBs original calibration is reported in Cornaro et

framed box was compared with the simulation

al., 2016. For the purpose of this study it was

data provided by the STB model to verify the old

necessary to reduce the glazed surface to control

calibration accuracy. Root mean square error

solar irradiance entering into the boxes. In this way

(RMSE) and normalized RMSE, NMRSE, were used

PCM was not exposed to too high temperature that

to evaluate the accuracy. The two indexes are

Cristina Cornaro, Marco Pierro, Daniele Roncarati, Valerio Adoo Puggioni

2.4 Measurement campaigns Two measurement campaigns were carried out, each of them including three full days of data acquisition.

2.4.1

First campaign

The first campaign was conducted from the 26 th to the 29th of September 2016. Two boxes were exposed outdoor, one with a PCM pane layered on Fig. 2 – Temperature trends recorded during the calibration of the new frame (NF); OF = original frame; ext = outside air

the box floor (PCM box) and the other one without PCM (Ref box). Air temperature inside both boxes was

defined as:

measured

together

with

outdoor

air

temperature, relative humidity, wind speed and direction and global irradiance on a vertical plane. 𝑚 𝑠 2 ∑n i=1(𝑥𝑖 −𝑥𝑖 )

RMSE = √ NRMSE =

n 𝑅𝑀𝑆𝐸

𝑚 −𝑥 𝑚 𝑥𝑚𝑎𝑥 𝑚𝑖𝑛

Climatic conditions during the test are presented in (1)

Figure 4 where air temperature (Tair_ext) and solar irradiance measured on a vertical plane (GR_V) are

(2)

showed. Good weather conditions characterized the period with high temperatures (maximum peak at 29 °C) and a significant thermal range between

A RMSE of 2.72 °C was obtained over the whole

day and night (12 – 13 °C). Solar irradiance reached

period of test with a NRMSE of 4% indicating a

peaks of approximately 800 W/m2.

good agreement with the original calibration.

Figure 5 shows the air temperature trends inside

To calibrate the new framed box the inside air

the reference box (Tair_ref) and the PCM box

temperature obtained by the STB simulation model

(Tair_PCM) during the test. A significant decrease

was compared with the experimental data; the U-

in maximum temperature is observed in PCM box

value of the frame and the ratio of opaque over

with respect to Ref box due to PCM melting in the

glazed area (frame fraction) were changed in the

temperature range 22 – 23 °C. An average decrease

model till the RMSE reached a minimum. Figure 3

of the temperature peaks of approximately 10 °C is

shows the inside air temperature trends of the new

observed during the day while at night an opposite

framed STB after calibration. A RMSE of 2.56 °C

behavior occurs. Indeed, air temperature inside

was obtained with a NRMSE of 5.4% considering a

PCM box is higher than in Ref box due to PCM

U = 2 W/m2K and a frame fraction, F = 0.55.

solidification and thermal mass.

Fig. 3 – Comparison between measured and simulated temperature trends inside the new framed box after calibration

Fig. 4 – Outdoor air temperature and global irradiance on a vertical plane experienced during the first measurement campaign.

Validation of a PCM simulation tool in IDA ICE dynamic building simulation software using experimental data

Fig. 5 – Air temperature inside the Ref box and the PCM box during the first test.

Fig. 7 – Air temperature inside the Ref box and the PCM box during the second test.

No evident shift of the temperature trend due to

Also in this case a temperature peak damping of

PCM heat capacity is observed, that is because the

approximately 10 °C caused by the PCM is

amount of material into the box is not enough to

observed during the clear days while for the

produce this effect.

overcast day no effect of the material is observed

2.4.2

due to the low temperatures experienced inside the

Second campaign

box (well below melting point). PCM solidification

A second measurement campaign was carried on

occurs earlier in the day (around 7 pm) than in the

later, in winter, between the 5

of

first campaign (around midnight). Apart from this

December 2016. Nice weather was experienced

shift, also a change in the curvature of the

during the last two days of test while the first day

decreasing temperature trend with respect to the

was overcast but not rainy, as evidenced by Figure

first campaign is observed. This is probably due to

6. Outdoor air temperature, in this case, was lower

the behavior of the solid phase at temperatures

than the first campaign with a maximum of

well below the solidification.

approximately

21

°C

and

th

a

and the 9

minimum

th

of

approximately 2 °C with a thermal range of 15 °C in the clear days. Solar irradiance reached values as high as 930 W/m2. This is because in this period

2.5 Simulation 2.5.1

STB model

sun elevation is low so a vertical surface receives

STBs were simulated in the IDA ICE environment.

higher irradiance than a horizontal one.

Geographic location corresponded to ESTER lab

Figure 7 shows the temperature trends inside Ref

coordinates and for all the simulations customized

and PCM boxes.

climate files were built using weather data coming from the weather and solar station of the same lab. Boxes were oriented with the glazing area toward the South. Thermal properties presented in Table 2 were inserted into the model. For what concerns the STB provided with the PCM the custom software module was connected to the STB floor working in advanced level mode. More detailed description of all input settings can be found in Cornaro et al. 2016.

2.5.2 Fig. 6 – Outdoor air temperature and global irradiance on a vertical plane experienced during the second measurement campaign.

Custom PCM software module description

“PCM wall” is a module for IDA ICE, written in NMF language (Neutral Model Format), that

Cristina Cornaro, Marco Pierro, Daniele Roncarati, Valerio Adoo Puggioni

allows calculating heat absorbed and/or released

in which the PCM behaved in different ways due

by phase change materials. It uses an enthalpy

to different climatic conditions. During the first

formulation to describe the relation between

campaign, in the month of September, the weather

enthalpy and temperature for a PCM material with

conditions were such that the PCM material could

different paths during melting and solidifying

work fully in its phase change temperature range,

phases. The partial enthalpies and the temperature

while in the month of December, even if solar

coordinates are input parameter vectors describing

irradiance was high, external air temperature limits

this relation. Partial enthalpies are expressed in

the PCM phase status mainly to solid for most of

J/kg. Heat capacity (J/(kgK)) is calculated dividing

the period. Figures 9 A and B show the comparison

partial

different

between experimental and simulated temperature

temperatures by the correspondent temperature

enthalpies

difference

at

trends inside the PCM box for the campaign of

interval.

September and December, respectively. A very

The computed help variable “Mode” is used to

good agreement can be observed for both periods

keep track of current state (phase) of the PCM

indicating the correct simulation of the boxes and

material.

the PCM. In Figure 9B a major difference between

There are five different PCM conditions that can be

experimental

monitored with the variable "Mode”, for which

observed

heat capacity, thermal resistance and temperature

temperature inside the PCM box falls down to 18

as a function of enthalpy are computed: Mode -2: solid phase

°C. In this period the PCM material is in the solid

and

during

simulated the

night

temperature when

the

is air

phase and it continues to cool down. The model

-

Mode 2: liquid phase

does not seem to follow the experimental trend as

-

Mode -1: solidifying phase

well as during the first campaign and this is

-

Mode 0: reversing during

probably

melting/solidifying phase

specifications are not available in the model for

Mode 1: melting phase

such low temperatures.

-

due

to

the

fact

that

the

PCM

Figure 8 shows the enthalpy versus temperature curves, as specified by RUBITHERM® for the SP21 PCM pane, for heating and cooling. These data were input to the PCM software module.

Fig. 8 – Enthalpy - temperature curves for heating and cooling for SP21 PCM pane tested.

3. Discussion and Results Experimental

data

gathered

during

the

two

experimental campaigns were used to validate the custom PCM software module having two datasets

Fig. 9 – Measured and simulated air temperature, inside the PCM box for the first (A) and second (B) monitoring campaign.

Validation of a PCM simulation tool in IDA ICE dynamic building simulation software using experimental data

During the overcast day temperatures were too

of approximately 10 °C.

low so that the PCM always stayed in the solid

During the night it releases heat (4-5 W) due to

phase. To quantify the accuracy of simulation,

solidification. While during the first campaign it

RMSE and NMRSE were evaluated for all cases

stays in the liquid phase all daytime and in solid

and are listed in Table 3. In the calculations the

phase during night, in the second campaign it is

first and last hours of operation were discarded to

mainly in the solid phase due to low outside

evaluate the indexes on three full days for each

temperatures, melting occurring only between

campaign. Also the indexes referred to Ref box

11:00 am and 6:00 pm.

were evaluated to verify the correct simulation of the box itself. It can be noted as NRMSE stays below 6% for all cases confirming the optimum

4. Conclusion

agreement. A method to validate a custom made software Table 3 – RMSE and NMRSE between measured and simulated temperature trends for the two campaigns

Campaign

Ref box

PCM box

RMSE

NMRSE

RMSE

NMRSE

(°C)

(%)

(°C)

(%)

26-29/09/16

1.78

4.1

1.57

5.0

05-12/12/16

2.50

5.2

1.83

5.1

Figure 10 A and B show the heat fluxes (HF) of PCM and of incoming solar radiation together with the temperature experienced by PCM simulated for the two monitoring campaigns. The pane removes approximately 15 W peak during the day compared to an incoming solar flux with peaks of around 40 W (around 40% of heat reduction) lowering the box air temperature peaks

module to simulate PCM materials has been presented. The software module has been built in the IDA ICE environment and experimental data for validation were collected in two outdoor monitoring campaigns using solar text boxes. A different behaviour of the PCM could be observed due to different climate conditions during the two campaigns. A very good agreement between measured and simulated temperature trends inside the boxes have been observed proving the good implementation

of

the

customized

software

module. Small discrepancies were only identified during night time for the December campaign probably due to lack of information on PCM behaviour at such low temperatures in the solid phase. However, this does not invalidate the results obtained. Also analysis of heat fluxes has been carried on using the validated model. Future work will consist in the energy saving capability evaluation of PCM materials implemented into office buildings.

References Barreneche C, Navarro ME, Ines Fernandez A, Cabeza LF. 2013. “Improvement of the thermal inertia of building materials incorporation PCM. Evaluation in the macroscale.” Applied Energy 109:428–432. Behzadi S., Farid MM. 2011. “Experimental and numerical investigations on the effect of using phase change materials for energy conservation in residential buildings.” HVAC & R Research 17(3):366–76. Fig. 10 – Heat flux (HF) of PCM and of incoming solar radiation and temperature trend of the PCM. A: first test; B: second test.

Bontemps A., Ahmad M., Johannès K., Sallée H.

Cristina Cornaro, Marco Pierro, Daniele Roncarati, Valerio Adoo Puggioni

2011 “Experimental and modelling study of

of passive application of PCM in Spain.” I

twin cells with latent heat storage walls.”

Congreso

Energy and Buildings 43: 2456–2461.

Edificación,

Diaconu BM, Cruceru M. 2010. “Novel concept of

Internacional

de

Investigación

24/06/2009-26/06/2009,

en

Madrid,

España.

composite phase change material wall system

Sage-Lauck JS, Sailor DJ. 2014. “Evaluation of

for year-round thermal energy savings.” Energy

phase change materials for improving thermal

and Buildings 42:1759–72.

comfort

Entrop A.G., Brouwers H.J.H., Reinders A.H.M.E. 2011. “Experimental research on the use of

in

a

super-insulated

residential

building.” Energy and Buildings 79:32–40. Souayfane F., Fardoun F., Biwole P-H. 2016. “Phase

micro-encapsulated Phase Change Materials to

change

store solar energy in concrete floors and to save

applications in buildings: A review.” Energy and

energy in Dutch houses.” Solar Energy 85: 1007– 1020.

materials

(PCM)

for

cooling

Buildings 129: 396–431. Su J.F., Wang X.Y., Wang S.B., Zhao Y.H., Huang Z.

Fernandez NTA, Costa VAF. 2009. “Use of phase-

2012.

“Fabrication

and

properties

of

change materials as passive elements for

microencapsulated-paraffin/gypsum-matrix

climatization

building materials for thermal energy storage."

purposes

in

summer:

the

Portuguese case.” International Journal of Green Energy 6(3):302–311.

Energy Conversion and Management 55:101–107. Tardieu A., Behzadi S., Chenand J. J.J, Farid M. M.

Goia F., Perino M., Serra V. 2014. “Experimental

2011. “Computer simulation and experimental

analysis of the energy performance of a full-

measurements

scale PCM glazing prototype.” Solar Energy 100:

impregnated office building. Proceedings of

217–233.

Building Simulation 2011. 12th Conference of

Guarino F., Dermardiros V., Chen Y., Rao J., Athienitis A., Cellura M., Mistretta M. 2015.

for

an

experimental

PCM-

International Building Performance Simulation Association, Sydney, 14-16 November.

“PCM thermal energy storage in buildings:

Telkes, M. 1975. “Thermal Storage For Solar

experimental study and applications”. Energy

Heating And Cooling.” Proceeding of the

Procedia 70: 219 – 228.

workshop on Solar Energy Storage Subsystems

Khadiran T., Hussein M. Z., Zainal Z., Rusli R. 2016. “Advanced energy storage materials for building

applications

performance

and

their

characterization:

a

for the Heating and cooling of Buildings, Charlottesville (Virginia, USA).

thermal

Zhang GH, Bon SAF, Zhao CY. 2012. “Synthesis,

review.”

characterization and thermal properties of

Renewable and Sustainable Energy Reviews 57:

novel

916–928.

materials for thermal energy storage.” Solar

Lee SH,Yoon SJ, Kim YG, Choi YC, Kim JH, Lee JG. 2007. “Development of building materials by using

micro-encapsulated

phase

nano

encapsulated

phase

change

Energy 86:1149–1154. Zhou D, Shire GSF, Tian Y. 2014. “Parametric

change

analysis of influencing factors in phase change

material.” Korean Journal of Chemical Engineering

material wallboard (PCMW).” Applied Energy

24(2):332–5.

19:33–42.

Li M, Wu Z, Tan J. 2013. “Heat storage properties of

the

cement

mortar

incorporated

with

Zhang Z, Shi G, Wang S, Fang X, Liu X. 2013. “Thermal

energy

storage

cement

containing

Energy 103:393–399.

composite phase change material.” Renewable

Marchi

S,

Pagliolico

“Characterization

S, of

Sassi panels

G.

2013.

n-octadecane/expanded

mortar

composite phase change material.” Applied

graphite

Energy 50:670–675.

containing

Zwanzig SD, Lian Y, Brehob EG. 2013. “Numerical

microencapsulated phase change materials.”

simulation of phase change material composite

Energy Conversion and Management 74:261–268.

wallboard

Rodríguez Ubiñas, E.*, Cronemberger, J., Vega Sánchez, S. and García Santos, A. “Performance

envelope.”

in

a

multi-layered

Energy

Management 69:27–40.

Conversion

building and